/*
 * Copyright (c) 2007, 2015, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
/*
 * Copyright 1999-2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
// $Id: XPathImpl.java,v 1.2 2005/08/16 22:41:08 jeffsuttor Exp $

package com.sun.org.apache.xpath.internal.jaxp;

import javax.xml.namespace.QName;
import javax.xml.namespace.NamespaceContext;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathFunctionResolver;
import javax.xml.xpath.XPathVariableResolver;
import javax.xml.xpath.XPathExpression;

import com.sun.org.apache.xml.internal.dtm.DTM;
import com.sun.org.apache.xpath.internal.*;
import com.sun.org.apache.xpath.internal.objects.XObject;
import com.sun.org.apache.xpath.internal.res.XPATHErrorResources;
import com.sun.org.apache.xalan.internal.res.XSLMessages;
import com.sun.org.apache.xalan.internal.utils.FactoryImpl;
import com.sun.org.apache.xalan.internal.utils.FeatureManager;

import org.w3c.dom.Node;
import org.w3c.dom.Document;
import org.w3c.dom.traversal.NodeIterator;

import org.xml.sax.InputSource;
import org.xml.sax.SAXException;

import javax.xml.parsers.*;

import java.io.IOException;

/**
 * The XPathImpl class provides implementation for the methods defined  in
 * javax.xml.xpath.XPath interface. This provide simple access to the results
 * of an XPath expression.
 *
 * @author Ramesh Mandava
 * @version $Revision: 1.10 $
 */
public class XPathImpl implements javax.xml.xpath.XPath {

  // Private variables
  private XPathVariableResolver variableResolver;
  private XPathFunctionResolver functionResolver;
  private XPathVariableResolver origVariableResolver;
  private XPathFunctionResolver origFunctionResolver;
  private NamespaceContext namespaceContext = null;
  private JAXPPrefixResolver prefixResolver;
  // By default Extension Functions are allowed in XPath Expressions. If
  // Secure Processing Feature is set on XPathFactory then the invocation of
  // extensions function need to throw XPathFunctionException
  private boolean featureSecureProcessing = false;
  private boolean useServiceMechanism = true;
  private final FeatureManager featureManager;

  XPathImpl(XPathVariableResolver vr, XPathFunctionResolver fr) {
    this(vr, fr, false, true, new FeatureManager());
  }

  XPathImpl(XPathVariableResolver vr, XPathFunctionResolver fr,
      boolean featureSecureProcessing, boolean useServiceMechanism,
      FeatureManager featureManager) {
    this.origVariableResolver = this.variableResolver = vr;
    this.origFunctionResolver = this.functionResolver = fr;
    this.featureSecureProcessing = featureSecureProcessing;
    this.useServiceMechanism = useServiceMechanism;
    this.featureManager = featureManager;
  }

  /**
   * <p>Establishes a variable resolver.</p>
   *
   * @param resolver Variable Resolver
   */
  public void setXPathVariableResolver(XPathVariableResolver resolver) {
    if (resolver == null) {
      String fmsg = XSLMessages.createXPATHMessage(
          XPATHErrorResources.ER_ARG_CANNOT_BE_NULL,
          new Object[]{"XPathVariableResolver"});
      throw new NullPointerException(fmsg);
    }
    this.variableResolver = resolver;
  }

  /**
   * <p>Returns the current variable resolver.</p>
   *
   * @return Current variable resolver
   */
  public XPathVariableResolver getXPathVariableResolver() {
    return variableResolver;
  }

  /**
   * <p>Establishes a function resolver.</p>
   *
   * @param resolver XPath function resolver
   */
  public void setXPathFunctionResolver(XPathFunctionResolver resolver) {
    if (resolver == null) {
      String fmsg = XSLMessages.createXPATHMessage(
          XPATHErrorResources.ER_ARG_CANNOT_BE_NULL,
          new Object[]{"XPathFunctionResolver"});
      throw new NullPointerException(fmsg);
    }
    this.functionResolver = resolver;
  }

  /**
   * <p>Returns the current function resolver.</p>
   *
   * @return Current function resolver
   */
  public XPathFunctionResolver getXPathFunctionResolver() {
    return functionResolver;
  }

  /**
   * <p>Establishes a namespace context.</p>
   *
   * @param nsContext Namespace context to use
   */
  public void setNamespaceContext(NamespaceContext nsContext) {
    if (nsContext == null) {
      String fmsg = XSLMessages.createXPATHMessage(
          XPATHErrorResources.ER_ARG_CANNOT_BE_NULL,
          new Object[]{"NamespaceContext"});
      throw new NullPointerException(fmsg);
    }
    this.namespaceContext = nsContext;
    this.prefixResolver = new JAXPPrefixResolver(nsContext);
  }

  /**
   * <p>Returns the current namespace context.</p>
   *
   * @return Current Namespace context
   */
  public NamespaceContext getNamespaceContext() {
    return namespaceContext;
  }

  private static Document d = null;

  private DocumentBuilder getParser() {
    try {
      // we'd really like to cache those DocumentBuilders, but we can't because:
      // 1. thread safety. parsers are not thread-safe, so at least
      //    we need one instance per a thread.
      // 2. parsers are non-reentrant, so now we are looking at having a
      // pool of parsers.
      // 3. then the class loading issue. The look-up procedure of
      //    DocumentBuilderFactory.newInstance() depends on context class loader
      //    and system properties, which may change during the execution of JVM.
      //
      // so we really have to create a fresh DocumentBuilder every time we need one
      // - KK
      DocumentBuilderFactory dbf = FactoryImpl.getDOMFactory(useServiceMechanism);
      dbf.setNamespaceAware(true);
      dbf.setValidating(false);
      return dbf.newDocumentBuilder();
    } catch (ParserConfigurationException e) {
      // this should never happen with a well-behaving JAXP implementation.
      throw new Error(e);
    }
  }


  private XObject eval(String expression, Object contextItem)
      throws javax.xml.transform.TransformerException {
    com.sun.org.apache.xpath.internal.XPath xpath = new com.sun.org.apache.xpath.internal.XPath(
        expression,
        null, prefixResolver, com.sun.org.apache.xpath.internal.XPath.SELECT);
    com.sun.org.apache.xpath.internal.XPathContext xpathSupport = null;
    if (functionResolver != null) {
      JAXPExtensionsProvider jep = new JAXPExtensionsProvider(
          functionResolver, featureSecureProcessing, featureManager);
      xpathSupport = new com.sun.org.apache.xpath.internal.XPathContext(jep);
    } else {
      xpathSupport = new com.sun.org.apache.xpath.internal.XPathContext();
    }

    XObject xobj = null;

    xpathSupport.setVarStack(new JAXPVariableStack(variableResolver));

    // If item is null, then we will create a a Dummy contextNode
    if (contextItem instanceof Node) {
      xobj = xpath.execute(xpathSupport, (Node) contextItem,
          prefixResolver);
    } else {
      xobj = xpath.execute(xpathSupport, DTM.NULL, prefixResolver);
    }

    return xobj;
  }

  /**
   * <p>Evaluate an <code>XPath</code> expression in the specified context and return the result as
   * the specified type.</p>
   *
   * <p>See "Evaluation of XPath Expressions" section of JAXP 1.3 spec for context item evaluation,
   * variable, function and <code>QName</code> resolution and return type conversion.</p>
   *
   * <p>If <code>returnType</code> is not one of the types defined in {@link XPathConstants} (
   * {@link XPathConstants#NUMBER NUMBER}, {@link XPathConstants#STRING STRING}, {@link
   * XPathConstants#BOOLEAN BOOLEAN}, {@link XPathConstants#NODE NODE} or {@link
   * XPathConstants#NODESET NODESET}) then an <code>IllegalArgumentException</code> is thrown.</p>
   *
   * <p>If a <code>null</code> value is provided for <code>item</code>, an empty document will be
   * used for the context. If <code>expression</code> or <code>returnType</code> is
   * <code>null</code>, then a <code>NullPointerException</code> is thrown.</p>
   *
   * @param expression The XPath expression.
   * @param item The starting context (node or node list, for example).
   * @param returnType The desired return type.
   * @return Result of evaluating an XPath expression as an <code>Object</code> of
   * <code>returnType</code>.
   * @throws XPathExpressionException If <code>expression</code> cannot be evaluated.
   * @throws IllegalArgumentException If <code>returnType</code> is not one of the types defined in
   * {@link XPathConstants}.
   * @throws NullPointerException If <code>expression</code> or <code>returnType</code> is
   * <code>null</code>.
   */
  public Object evaluate(String expression, Object item, QName returnType)
      throws XPathExpressionException {
    if (expression == null) {
      String fmsg = XSLMessages.createXPATHMessage(
          XPATHErrorResources.ER_ARG_CANNOT_BE_NULL,
          new Object[]{"XPath expression"});
      throw new NullPointerException(fmsg);
    }
    if (returnType == null) {
      String fmsg = XSLMessages.createXPATHMessage(
          XPATHErrorResources.ER_ARG_CANNOT_BE_NULL,
          new Object[]{"returnType"});
      throw new NullPointerException(fmsg);
    }
    // Checking if requested returnType is supported. returnType need to
    // be defined in XPathConstants
    if (!isSupported(returnType)) {
      String fmsg = XSLMessages.createXPATHMessage(
          XPATHErrorResources.ER_UNSUPPORTED_RETURN_TYPE,
          new Object[]{returnType.toString()});
      throw new IllegalArgumentException(fmsg);
    }

    try {

      XObject resultObject = eval(expression, item);
      return getResultAsType(resultObject, returnType);
    } catch (java.lang.NullPointerException npe) {
      // If VariableResolver returns null Or if we get
      // NullPointerException at this stage for some other reason
      // then we have to reurn XPathException
      throw new XPathExpressionException(npe);
    } catch (javax.xml.transform.TransformerException te) {
      Throwable nestedException = te.getException();
      if (nestedException instanceof javax.xml.xpath.XPathFunctionException) {
        throw (javax.xml.xpath.XPathFunctionException) nestedException;
      } else {
        // For any other exceptions we need to throw
        // XPathExpressionException ( as per spec )
        throw new XPathExpressionException(te);
      }
    }

  }

  private boolean isSupported(QName returnType) {
    if ((returnType.equals(XPathConstants.STRING)) ||
        (returnType.equals(XPathConstants.NUMBER)) ||
        (returnType.equals(XPathConstants.BOOLEAN)) ||
        (returnType.equals(XPathConstants.NODE)) ||
        (returnType.equals(XPathConstants.NODESET))) {

      return true;
    }
    return false;
  }

  private Object getResultAsType(XObject resultObject, QName returnType)
      throws javax.xml.transform.TransformerException {
    // XPathConstants.STRING
    if (returnType.equals(XPathConstants.STRING)) {
      return resultObject.str();
    }
    // XPathConstants.NUMBER
    if (returnType.equals(XPathConstants.NUMBER)) {
      return new Double(resultObject.num());
    }
    // XPathConstants.BOOLEAN
    if (returnType.equals(XPathConstants.BOOLEAN)) {
      return new Boolean(resultObject.bool());
    }
    // XPathConstants.NODESET ---ORdered, UNOrdered???
    if (returnType.equals(XPathConstants.NODESET)) {
      return resultObject.nodelist();
    }
    // XPathConstants.NODE
    if (returnType.equals(XPathConstants.NODE)) {
      NodeIterator ni = resultObject.nodeset();
      //Return the first node, or null
      return ni.nextNode();
    }
    String fmsg = XSLMessages.createXPATHMessage(
        XPATHErrorResources.ER_UNSUPPORTED_RETURN_TYPE,
        new Object[]{returnType.toString()});
    throw new IllegalArgumentException(fmsg);
  }


  /**
   * <p>Evaluate an XPath expression in the specified context and return the result as a
   * <code>String</code>.</p>
   *
   * <p>This method calls {@link #evaluate(String expression, Object item, QName returnType)} with a
   * <code>returnType</code> of {@link XPathConstants#STRING}.</p>
   *
   * <p>See "Evaluation of XPath Expressions" of JAXP 1.3 spec for context item evaluation,
   * variable, function and QName resolution and return type conversion.</p>
   *
   * <p>If a <code>null</code> value is provided for <code>item</code>, an empty document will be
   * used for the context. If <code>expression</code> is <code>null</code>, then a
   * <code>NullPointerException</code> is thrown.</p>
   *
   * @param expression The XPath expression.
   * @param item The starting context (node or node list, for example).
   * @return The <code>String</code> that is the result of evaluating the expression and converting
   * the result to a <code>String</code>.
   * @throws XPathExpressionException If <code>expression</code> cannot be evaluated.
   * @throws NullPointerException If <code>expression</code> is <code>null</code>.
   */
  public String evaluate(String expression, Object item)
      throws XPathExpressionException {
    return (String) this.evaluate(expression, item, XPathConstants.STRING);
  }

  /**
   * <p>Compile an XPath expression for later evaluation.</p>
   *
   * <p>If <code>expression</code> contains any {@link XPathFunction}s, they must be available via
   * the {@link XPathFunctionResolver}. An {@link XPathExpressionException} will be thrown if the
   * <code>XPathFunction</code> cannot be resovled with the <code>XPathFunctionResolver</code>.</p>
   *
   * <p>If <code>expression</code> is <code>null</code>, a <code>NullPointerException</code> is
   * thrown.</p>
   *
   * @param expression The XPath expression.
   * @return Compiled XPath expression.
   * @throws XPathExpressionException If <code>expression</code> cannot be compiled.
   * @throws NullPointerException If <code>expression</code> is <code>null</code>.
   */
  public XPathExpression compile(String expression)
      throws XPathExpressionException {
    if (expression == null) {
      String fmsg = XSLMessages.createXPATHMessage(
          XPATHErrorResources.ER_ARG_CANNOT_BE_NULL,
          new Object[]{"XPath expression"});
      throw new NullPointerException(fmsg);
    }
    try {
      com.sun.org.apache.xpath.internal.XPath xpath = new XPath(expression, null,
          prefixResolver, com.sun.org.apache.xpath.internal.XPath.SELECT);
      // Can have errorListener
      XPathExpressionImpl ximpl = new XPathExpressionImpl(xpath,
          prefixResolver, functionResolver, variableResolver,
          featureSecureProcessing, useServiceMechanism, featureManager);
      return ximpl;
    } catch (javax.xml.transform.TransformerException te) {
      throw new XPathExpressionException(te);
    }
  }


  /**
   * <p>Evaluate an XPath expression in the context of the specified <code>InputSource</code> and
   * return the result as the specified type.</p>
   *
   * <p>This method builds a data model for the {@link InputSource} and calls {@link
   * #evaluate(String expression, Object item, QName returnType)} on the resulting document
   * object.</p>
   *
   * <p>See "Evaluation of XPath Expressions" section of JAXP 1.3 spec for context item evaluation,
   * variable, function and QName resolution and return type conversion.</p>
   *
   * <p>If <code>returnType</code> is not one of the types defined in {@link XPathConstants}, then
   * an <code>IllegalArgumentException</code> is thrown.</p>
   *
   * <p>If <code>expression</code>, <code>source</code> or <code>returnType</code> is
   * <code>null</code>, then a <code>NullPointerException</code> is thrown.</p>
   *
   * @param expression The XPath expression.
   * @param source The input source of the document to evaluate over.
   * @param returnType The desired return type.
   * @return The <code>Object</code> that encapsulates the result of evaluating the expression.
   * @throws XPathExpressionException If expression cannot be evaluated.
   * @throws IllegalArgumentException If <code>returnType</code> is not one of the types defined in
   * {@link XPathConstants}.
   * @throws NullPointerException If <code>expression</code>, <code>source</code> or
   * <code>returnType</code> is <code>null</code>.
   */
  public Object evaluate(String expression, InputSource source,
      QName returnType) throws XPathExpressionException {
    // Checking validity of different parameters
    if (source == null) {
      String fmsg = XSLMessages.createXPATHMessage(
          XPATHErrorResources.ER_ARG_CANNOT_BE_NULL,
          new Object[]{"source"});
      throw new NullPointerException(fmsg);
    }
    if (expression == null) {
      String fmsg = XSLMessages.createXPATHMessage(
          XPATHErrorResources.ER_ARG_CANNOT_BE_NULL,
          new Object[]{"XPath expression"});
      throw new NullPointerException(fmsg);
    }
    if (returnType == null) {
      String fmsg = XSLMessages.createXPATHMessage(
          XPATHErrorResources.ER_ARG_CANNOT_BE_NULL,
          new Object[]{"returnType"});
      throw new NullPointerException(fmsg);
    }

    //Checking if requested returnType is supported.
    //returnType need to be defined in XPathConstants
    if (!isSupported(returnType)) {
      String fmsg = XSLMessages.createXPATHMessage(
          XPATHErrorResources.ER_UNSUPPORTED_RETURN_TYPE,
          new Object[]{returnType.toString()});
      throw new IllegalArgumentException(fmsg);
    }

    try {

      Document document = getParser().parse(source);

      XObject resultObject = eval(expression, document);
      return getResultAsType(resultObject, returnType);
    } catch (SAXException e) {
      throw new XPathExpressionException(e);
    } catch (IOException e) {
      throw new XPathExpressionException(e);
    } catch (javax.xml.transform.TransformerException te) {
      Throwable nestedException = te.getException();
      if (nestedException instanceof javax.xml.xpath.XPathFunctionException) {
        throw (javax.xml.xpath.XPathFunctionException) nestedException;
      } else {
        throw new XPathExpressionException(te);
      }
    }

  }


  /**
   * <p>Evaluate an XPath expression in the context of the specified <code>InputSource</code> and
   * return the result as a <code>String</code>.</p>
   *
   * <p>This method calls {@link #evaluate(String expression, InputSource source, QName returnType)}
   * with a <code>returnType</code> of {@link XPathConstants#STRING}.</p>
   *
   * <p>See "Evaluation of XPath Expressions" section of JAXP 1.3 spec for context item evaluation,
   * variable, function and QName resolution and return type conversion.</p>
   *
   * <p>If <code>expression</code> or <code>source</code> is <code>null</code>, then a
   * <code>NullPointerException</code> is thrown.</p>
   *
   * @param expression The XPath expression.
   * @param source The <code>InputSource</code> of the document to evaluate over.
   * @return The <code>String</code> that is the result of evaluating the expression and converting
   * the result to a <code>String</code>.
   * @throws XPathExpressionException If expression cannot be evaluated.
   * @throws NullPointerException If <code>expression</code> or <code>source</code> is
   * <code>null</code>.
   */
  public String evaluate(String expression, InputSource source)
      throws XPathExpressionException {
    return (String) this.evaluate(expression, source, XPathConstants.STRING);
  }

  /**
   * <p>Reset this <code>XPath</code> to its original configuration.</p>
   *
   * <p><code>XPath</code> is reset to the same state as when it was created with
   * {@link XPathFactory#newXPath()}.
   * <code>reset()</code> is designed to allow the reuse of existing <code>XPath</code>s
   * thus saving resources associated with the creation of new <code>XPath</code>s.</p>
   *
   * <p>The reset <code>XPath</code> is not guaranteed to have the same
   * {@link XPathFunctionResolver}, {@link XPathVariableResolver}
   * or {@link NamespaceContext} <code>Object</code>s, e.g. {@link Object#equals(Object obj)}.
   * It is guaranteed to have a functionally equal <code>XPathFunctionResolver</code>,
   * <code>XPathVariableResolver</code>
   * and <code>NamespaceContext</code>.</p>
   */
  public void reset() {
    this.variableResolver = this.origVariableResolver;
    this.functionResolver = this.origFunctionResolver;
    this.namespaceContext = null;
  }

}
